Hydraulic weighing scale with temperature compensating means



Nov. 16, 1,943 1 R. $1BO'HANNAN 2,334,242]

HYDRAULIC WE'JXHIING SCALE WITH TEMPERATURE COMPENSATING MEANS I Filed May 12-, 1941 3 Sheets-Shet 1 Poke/'7 5. Baku/man INVENTOR ATTORNEYS Nov. 16, 1943. R. s. BOHANNAN HYDRAULIC WEIGHING SCALE WITH TEMPERATURE COMPENSATING MEANS Filed May 12, 1941 '5 Sheets-Sheet 3 Robe/*7 5. 50/70/700 INVENTOR EATTORNEYS I v Patented Nov. 16, 1943 UNITED STATES PATENT OFFICE mamuc wnranmo scam wrrn rimmma'runs courassa'rmo means ration of New Jersey Application May 1941, Serial No. 393,012

9 Claims. (c1. ass-41) This invention relates to weighing scales of the type wherein the force transmission mechanism includes a hydraulic system, and more particularly to means for automatically compensating for the effect of temperature changes on the hydraulic liquidcontained in the hydraulic system.

A heavy duty weighing scale may be so placed that the platform, or load receiving portion of the scale, is in the open where it is exposed to temperature changes of many degrees during relatlvely short periods of time. when a heavy duty scale of the hydraulic type is exposed tosuch temperature changes, expansion and contraction of the liquid in the hydraulic system of the scale takes place. Expansion of the liquid result in application of a greater force to the load counterbalance, and the application to the load counterbalancing portion ofthe scale of the additional force created by expansion of the liquid must be counteracted by increased counter-force to bring the scale to balance. If such increased counterforce is applied by a weighing poise, the amount of the load being weighed is indicated erroneously.

It is an object of this invention to provide an automatic means whereby a force or pressure is applied to the load counterbalancing mechanism in a direction opposite to, and in an amount proportional to the increased force or pressure which is the result of the expansion of the liquid in the hydraulic system of the scale.

More specific objects and advantages are apparent from the description, in which reference is had to the accompanying drawing illustrating a preferred form of scale embodying the invention.

In the drawings:

Fig. I is a iront elevation of a scale embodying the invention. 7

Fig. 11 is an enlarged fragmentary front elevation of members connecting the hydraulic system to the load eounterbalancing means, certain portions being shown insection.

Fig. III is a vertical section taken on the line III-HI of Fig. H.

Fig. IV is a horizontal section taken on the line IV-IV of Fig. II, and illustrating the shell lever of the scale.

Fig. V is a front elevation of an alternate form of the invention, certain parts being shown in section.

Fig. VI is a section taken on the line VI-VI of. Fig. V.

Fig. VII is a front elevation of another alternate form of the invention. I

Fig. VIII is a vertical section taken on the line VIII-VIII Of F18. VII.

These specific drawings and the specific description that follows merely disclose and illustrate the invention and are not intended to impose limitations upon the claims. I

The specific details of the operation of the load receiving and force transmitting portions or a hydraulic scale are disclosed in my copending applications Serial Nos. 222,831-299,832 and 299,833.

A platform It is supported upon parallel link suspension devices Ii, which are in turn supported upon the upper plates of capsules [2 located in a scale pit l 3. Leading from the capsules 82 are pipe lines It, each one of which is connected to an individual chamber I! (Fig. II) mounted on a shelf of a stand it. Each of the capsules i2 has a corresponding pipe line It and chamber l5, thus forming an individual selfenclosed hydraulic system. Mounted inside of each of the chambers II is a metaliic'bellows I! through the open lower end of which extends a strut it. Each of the struts It has adjustably attached to its lower end a clevis I! in which ismountedabearing 20.

A shelf lever 2| is fulcrumed on a bearing 22 mounted in a bracket 23 which is attached to the stand it. The shelf lever 2i (Fig. IV) has mounted for rockable adjustment therein a series of pivots 24 which carry the bearing ZiLof the struts II. A nose pivot 25, mounted in the shelf lever 2i, engages a bearing 26 in the lower end of a vertically disposed pull rod 21, which passes through an opening in the stand it. The upper end of the pull rod 21 carries a bearing 23, which 'rests upon a load pivot 29 mounted in a counterbalancing beam 30. The beam 30 is fulcrumed upon a bearing 3| carried by a fulcrum stand 32 motmted on the stand it. The beam 30 (Fla.

I) has slidably mounted thereon poises 33, which the beam 30 and counterbalanced by the poises 33.

Iixpansionoi the liqu'd eontainedintheeapoules l2, pipes and chambers ll, due to a rise or the hydraulic liquid, there is mounted on the beam ll (Fig. II) a bracket 30 having iastmed thereto a horizontally disposed bellows 31 which isiiliedwithaliquid.

Attached to the end the bellows. opposite that which is bolted to the bracket 38, is a weight chamber 88 adapted to be sealed out" by means oi the addition 01' lead or other heavy material added through a hole I! which is closed with a plug 40. A dust cover II is mountedover the bellows l1 and weight chamber 38 to keep the parts clean.

The linear displacement oi. the end of the bellows 31 is in direct ratio to the volume change of the liquid in the hydraulic system of the scale. Thus, a weight attached to. the free end 0! the bellows will be moved in a direct ratio to such expansion and will exert an increased force on the beam in'proportion to such expansion. Since the amount of weight in the weight chamber 38 can be varied and "sealed out its movement compensates exactly for the variation 01' force applied to the beam due to volume changes of the liquid in the hydraulic system of the scale and eliminates the necessity of moving the noises 33 further on the beam 30 than is necessary to balance the exact amount of the load.

A modification oi the compensating means is shownin Figures V and VI wherein a bellows 31a is mounted on a bracket 38a and has a weight chamber 38a attached to its opposite end. Rotatably mounted on a pin 42, carried by two arms 43 attached to the weight chamber 38a, is a roller 44 which rolls in a way 45. The purpose oi! this roller 44 is to support the end of the bellows Ila, carrying the weight chamber 38a, and prevent it from sagging as the weight is extended. A-dust cover lla extends over the mechanism to protect it A second modification of the invention is shown in Figures VII and VIII. A bellows 31b is mounted on a bracket 36?) and has a plate 48 at its closed end. A horizontal arm 41, centrally attached to the plate 48, is pivotally connected to a fork 48 which is pivotally supported in a vertically disposed bracket 49 attached to the main bracket 38b.

' Pivotally connected to the lower end of the legs v connection point, the fork l8 acts as an amplifying lever and the movement of the weight It is greater than that of the plate 46 attached to the bellows 31?). Because of this amplification of movement, the weight 5| exerts a large force on assess:

thebeam ilthuspermittingalesserweighttobe ueedwhichcanbemoreeaeilyfsealedout."

'Ihe embodiments of the invention that have been dmd may be modified to meet various requirements.

Having described the invention, I claim: .1.Inaweighingacale,incombination,aload receiver, a load coimterbalancing device, a hydraulic system-tor transmitting force from said lead receiver to said load counterbalancing device, saidsystem containing a liquid transmission medium which is subject toexpansion and contraction with variations in temperature, a hollow expansible body coniining a quantity or a thermostatically expansible and contractible liquid, and means having a variable moment otiorce actuated by said hollow expansible body in response to volumetric changes in the liquid confined therein for applying a force on said lead counterbalancing device to compensate for eflects oi the expansion and contractionot the liquid in said hydraulic system.

2. In a weighing scale, in combination, a load receiver, a load counterhalancing device, a hydraulic'system for transmitting force from said lead receiver to said load counterbalancing device, said system containing a liquid transmission means, a hollow expansible body operatively connected to said load counterbalancing device and confining a quantity of a liquid and means actuated by said hollow expansible body for applying variable and precalculated force to said load counterbalancing device in a direction opposite to forces applied to said load counterbalancing device by changes in volume oi the liquid in said hydraulic system.

3. In a-weighing scale, in combination, a load transmission medium and actuated by said load receiver, a load counterbalancing device actuated by said hydraulic system in proportion to the movement oi said load receiver, a hollow expanslble body, confining a quantity oi a liquid, mounted on said load counterbalancing device, and a variable weight acting on said load counterbal ancing device and moved by said hollow expansible body in proportion to the expansion of the liquid in said hydraulic system.

4. In a weighing scale, in combination, a load.

receiver, a hydraulic force transmission system containing a liquid, pressure creating means acting on said hydraulic force transmission system and actuated by said load receiver, a load counterbalancing device actuated by the pressure in said hydraulic system in proportion to the load on said load receiver and a metallic bellows mounted at one end on said load counterbalancing device and containing a quantity of liquid, said bellows having a variable weight attached to its free end which weight applies a force on said lead counterbalancing device to compensate for the force applied on said load counterbalancing mechanism by expansion and contraction of the liquid in said hydraulic system.

5. In a device of the class described, in combination, a load receiver, a load counterbalancing device, a hydraulic system containing a liquid force transmission means for transmitting force from said load receiver to said load counterbalancing device and temperature compensating means comprising a hollow expansib-le member confining a quantity of a liquid and operatively connected to said load counterbalancing device, and a variable weight connected to said member and adapted, in response to .temperature caused volumetric changes in the liquid confined therein, to apply force to said load counterbalancing device in inverse proportion to the force applied thereto by volumetric changes in the liquid in said hydraulic system caused by changes in temperature.

6. In a weighing scale, in combination, a load receiver, a load counterbalancing device, a hydraulic system for transmitting force from said load receiver to said load counterbalancing device, said system containing a thermostatically expansible and contractible liquid transmission means, a hollow expansible body confining a quantity of a thermostatically expansible and contractible liquid, one end of said hollow expansible body being connected to said load counterbalancing device, and a variable weight attached to the free end of said hollow expansible body for applying force to said load counterbalancing device in proportion to the volumetric changes in the liquid confined in said body in a direction op"- posite to forces applied to said load counterbalancing device by volumetric changes of the liquid transmission means contained in said hydraulic system.

7. In a weighing scale, in combination, a load receiver, a load counterbalancing beam, a hydraulic system for transmitting force from said load receiver to said beam, a hollow expansible body confining a quantity of a thermostatically expansible and contractible liquid and being mounted on and attached at one end to said beam,

and a variable weight attached to the other end of said hollow expansible body, said hollow expansible body extending parallelly to the longitudinal axis of said beam.

8. In a device of the class described, in combination, a load receiver, a hydraulic system actuated thereby, a load counterbalancing 'device responsive to the pressure in said hydraulic sys-' tem, a metallic bellows confining a quantity of liquid mounted at one end on said load counterbalancing device, a variable weight attached to the free end of said bellows, and a supporting roller attached to said weight to prevent a distortion of said bellows upon its extension due to the expansion of the liquid confined therein.

9. In a device of the class described, in combination, a load receiver, a load counterbalancing device, a hydraulic system containing a liquid for transmitting force from said load receiver to said load counterbalancing device, a metallic bellows 

